1. Technical Field
The present invention relates in general to designing and simulating digital devices, modules and systems in a distributed simulation environment. In particular, the present invention relates to a method and system that improve a distributed simulation environment to allow for efficient monitoring and utilization of instrumentation events embedded with a simulation model. More particularly, the present invention relates to a method and system for resolving testcase collection inconsistencies between a testcase list which includes testcases that have triggered harvest events within a simulation model, and a harvest hit table which records harvest events that have been triggered during simulation of the simulation model.
2. Description of the Related Art
Verifying the logical correctness of a digital design and debugging the design, if necessary, are very important steps in most digital design processes. Logic networks are tested either by actually building networks or by simulating networks on a computer. As logic networks become highly complex, it becomes necessary to simulate a design before the design is actually built. This is especially true when the design is implemented as an integrated circuit, since the fabrication of integrated circuits requires considerable time and correction of mistakes is quite costly. The goal of digital design simulation is the verification of the logical correctness of the design.
In a typical automated design process that is supported by a conventional electronic computer-aided design (ECAD) system, a designer enters a high-level description utilizing a hardware description language (HDL), such as VHDL, producing a representation of the various circuit blocks and their interconnections. The ECAD system compiles the design description into a format that is best suited for simulation. A simulator is then utilized to verify the logical correctness of the design prior to developing a circuit layout.
A simulator is typically a software tool that operates on a digital representation, or simulation model of a circuit, and a list of input stimuli representing inputs of the digital system. A simulator generates a numerical representation of the response of the circuit which may then either be viewed on the display screen as a list of values or further interpreted, often by a separate software program, and presented on the display screen in graphical form. The simulator may be run either on a general purpose computer or on another piece of electronic apparatus, typically attached to a general purpose computer, specially designed for simulation. Simulators that run entirely in software on a general purpose computer will hereinafter be referred to as “software simulators”. Simulators that are run with the assistance of specially designed electronic apparatus will hereinafter be referred to as “hardware simulators”.
Usually, software simulators perform a very large number of calculations and operate slowly from the user's point of view. In order to optimize performance, the format of the simulation model is designed for very efficient use by the simulator. Hardware simulators, by nature, require that the simulation model comprising the circuit description be communicated in a specially designed format. In either case, a translation from an HDL description to a simulation format, hereinafter referred to as a simulation executable model, is required.
The complexity of modern digital circuits demands an enormous amount of resources dedicated to performing and processing simulation of various simulation models. As a result, it is common to employ so-called “batch simulation farms” consisting of hundreds to thousands of computers employing hardware and software simulators. These systems are usually connected to a shared network and run simulation jobs with respect to one or more digital designs. The large numbers of computers performing foreground or background simulation testing enables the large number of simulations required by modem designs to be performed in a timely manner.
A batch simulation farm often encompasses general-purpose computers at geographically separated sites. For example, computers at a locations in different states or countries can be coupled into a given batch simulation farm. Such geographic distribution of servers leads to difficulties in communication and coordination that should be considered when monitoring and utilizing instrumentation events within simulation models.
A batch simulation farm typically contains a number of general-purpose computers that perform as servers that create, distribute, and control the flow of simulation jobs throughout the batch simulation farm. These servers perform simulation jobs, whose nature varies with the specifics of the simulation methodology used and complexity of the digital device, which are then routed to simulation servers within the batch simulation farm for execution.
A simulation server executes the simulation job, taking note of any failures and communicates pass/fail results back to servers within the batch simulation farm for logging and failed testcase storage for eventual debug. To allow for execution of tests on a large number of distributed systems, batch simulation farms will typically utilize a so-called “shared file system”. A shared file system allows a number of disparate general-purpose computers to share a common file system that is located on shared disks in a central location. Examples of such file system are the Networked File System (NFS), the Andrew File System (AFS), and the Distributed File System (DFS). The shared files system is used to provide access to common control and data files used by the batch simulation farm.
In addition to a shared file system, a number of well known network communication protocols are typically employed within a batch simulation farm to enable distribution of files, communication and coordination of servers, and inter-process communication among other tasks. Examples of these protocols are such things as File Transfer Protocol or FTP, Sockets for direct network connections between processes on different computers, etc. These protocols are well know to those skilled in the art and are not specific to batch simulation farms, but rather are common to all networking in modem general purpose computers.
A batch simulation farm typically must run in a largely autonomous fashion on a full time basis. This is to allow for the continuous execution of simulation tests without requiring continuous user intervention and direction. This autonomous background execution of tests also makes it possible for so-called “cycle-stealing” on machines not specifically dedicated to simulation. That is to say, general-purpose computers that are normally used by users can execute simulation tests in a background mode. In this background mode, the simulation task can take advantage of the otherwise idle compute resources on a large number of user machines. In addition, it is common for a large number of different simulation models to be active within a batch simulation farm at a given time.
The need for autonomous execution of large numbers of simulation jobs for a wide range of different models leads to certain challenges in monitoring and controlling instrumentation events within these models that must be overcome. Among the challenges arising in a batch simulation farm environment is the need to provide a means to collect and store, with minimal redundancy, those testcases in which harvest events, occur. The present invention addresses such a need.